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Should I be using 175 cranks or 172.5(4 posts)

Should I be using 175 cranks or 172.5trailjerky
Jul 8, 2002 9:13 AM
What would be the correct size cranks for me. I'm 6 foot and ride a 58cm trek 5200. For some reason the bike came with 172.5 cranks when they are suppose to come with 175 (I think). should I have them switched out for the longer cranks?
Consider it extra ground clearance!!Quack
Jul 8, 2002 9:53 AM
I doubt that you will notice a tremendous difference between the two. I'm 5'8" and switch between three bikes set up with 170, 172.5, and 175 crank arms. I can't honestly say that I am faster on any one of the three. If you are long in the inseam for your height, you may benefit slightly. But then again, you would probably be going for the 177.5 or 180 if that were the case. I would just ride the 172.5 or ask the dealer if they would do the swap for free due to the factory mistake.
172.5 sounds reasonablelaffeaux
Jul 8, 2002 3:15 PM
A Trek 58cm is roughly equivalent to most other manufacturers 56cm. ANd a lot of 56cm bike swill come with 172.5 cranks. Unless you have a prefernce there's no big difference. Some people say longer cranks are faster, others say shorter cranks are faster, which means it probably does not matter. 2.5mm is about the thickness of a credit card.
172.5 sounds reasonablecollinsc
Jul 8, 2002 9:55 PM
2.5mm is about twice the thickness of a credit card, and remember that that 2.5mm is on the radius of the crank circle. multiply by two to find that the ends of the cranks are now a half cm farther apart.

I agree tho, mostly just a feel preference i think. you can argue easily that longer cranks have more leverage and that shorter ones spin faster (both huge 'duhs' accoring to really elementary newtonian physics) but the differece is really very small. find someone elses bikes with the larger cranks, and if you like em, switch, if not, dont.